The present invention relates to an image reading method, an image reading apparatus and a method of discriminating a defect of image data, and more particularly to an image reading method in which an image on an image recording medium such as film or the like (hereinafter referred to simply as “film”) is read by a visible light and also a scratch, a folding mark, or a foreign matter such as dirt, dust, grime or the like on the film (second optical defect) and a scratch, or a foreign matter such as dirt, dust, grime or the like in an optical path of an optical system (first optical defect) in the image reading apparatus are detected by a specified detecting light, for example, preferably an invisible light such as an infrared light or the like, and an image reading apparatus adapted to the image reading method and a method of discriminating a defect of image data.
Heretofore, the images recorded on photographic films such as negative films, positive (reversal) films (which are hereinafter also referred to simply as “films”) have been commonly printed on photographic light-sensitive materials such as photographic paper and the like by means of direct (analog) exposure in which the film image is projected onto the light-sensitive material to achieve its areal exposure.
A new technology has recently been introduced and this is a printer that relies upon digital exposure. Briefly, the image recorded on a film is read photoelectrically, converted to digital signals and subjected to various image processing schemes to produce image data for recording purposes; recording light that has been modulated in accordance with the image data is used to scan and expose a light-sensitive material to record an image. The printer operating on this principle has been commercialized as a digital printer.
In the digital printer, images are converted to digital image data which are processed to determine the exposing conditions for printing. Hence, the digital printer is capable of performing effective image processing operations such as the correction of washed-out highlights or flat shadows due to the taking of pictures with back light or an electronic flash, sharpening and the correction of color or density failure and this enables the production of high-quality prints that have been impossible to attain by the conventional direct exposure technique. In addition, not only the assembling of plural images and the dividing of a single image but also the compositing of characters on image can be performed by processing the image data and, as a result, prints can be outputted after various editing and/or processing operations have been performed in accordance with specific uses.
Having these features, the digital printer is basically composed of an image input machine having a scanner (image reading apparatus) that reads the image on a film photoelectrically and an image processing apparatus that processes the image read with the scanner to produce output image data (exposing conditions) as well as an image output machine having a printer that scans and exposes a light-sensitive material in accordance with the image data outputted from the image input machine to record an image (a latent image) and a processor that performs development and other necessary processing on the exposed light-sensitive material to produce a print.
In the above-described scanner, reading light issuing from a light source is allowed to be incident on film, from which projected light bearing the image recorded on the film is produced and focused by an imaging lens to form a sharp image on an image sensor such as a CCD sensor; the image is then read by photoelectric conversion and sent to the image processing apparatus as image data (i.e., signals) for the film after being optionally subjected to various image processing schemes.
In the image processing apparatus, image processing conditions are set on the basis of the image data read with the scanner and image processing as determined by the thus set conditions is performed on the read image data and the resulting output image data for image recording are sent to the printer.
In the printer, if it is of a type that relies upon exposure by scanning with an optical beam, this optical beam is modulated in accordance with the image data sent from the image processing apparatus and deflected in a main scanning direction as the light-sensitive material is transported in an auxiliary scanning direction perpendicular to the main scanning direction, whereby a latent image is formed as the result of exposure (printing) of the light-sensitive material with the image bearing optical beam. Development and other processing are then performed in the processor rendering the latent image visible to produce a print reproducing the image that was recorded on the film.
It is essential that the original of a print to be produced or the film should be in a good condition in order to secure a high-definition print reproducing a high-quality image thereon. The film is transported in a camera for photographing, a developing apparatus for development and a scanner for reading (printing). During the transport, the surfaces of the film are in sliding contact with support members of the camera, the developing apparatus or the scanner. As a result, a scratch may often be produced on a surface of the film. Further, the film is very often treated in an ordinary environment in which any particular air cleaning is not performed; hence, a foreign matter such as dirt, dust, grime or the like is likely to adhere to the surface thereof.
As described above, when the image recorded on the film is read with the scanner, reading light is allowed to be incident on the film to produce projected light that is photoelectrically read with the CCD sensor or the like. In this process, any foreign matter which adheres to the film surfaces or any damage thereof blocks out or diffuses the reading light (projected light) thereby reducing the quantity of light. In case of a deep scratch, the quantity of transmitted light of the reading light is increased to the contrary whereby the light intensity of the projected light incident on the CCD sensor becomes inappropriate and no longer corresponds to the image on the film.
As a result, a high-quality image can not be obtained, since the foreign matter or the scratch is reproduced like a shadow on the obtained image and the peripheral image portion of the scratch looks blurred on the obtained image.
To deal with the above-described problems, various methods have been proposed. For example, Japanese Patent Publication No. 2559970 discloses a technique.
In the technique, there are provided a method and apparatus for use in correcting influences of defects of a storage medium (image recording medium, namely, film) to an image stored in the film. This method and apparatus apply infrared ray energy and visible light ray energy to the film, detecting a resulting infrared ray energy distribution corresponding to each defect in correspondence with each position on the film, detect a visible light ray energy distribution in correspondence with each position on the film, and enhance the intensity of the visible light ray energy distribution in the position of interest up to a level which offsets the intensity of the infrared ray energy distribution in the position of interest when intensity of the thus detected infrared ray energy distribution is larger than a specified threshold value in each position on the film, or correct the visible light ray energy distribution in the position of interest by interpolation when the intensity of the thus detected infrared ray energy distribution is smaller than the specified threshold value to the contrary, thereby correcting the effects of defects of the film.
In the digital printer, there exists another problem that dust enters an optical path in the printer itself or a member in the optical path is damaged; hence, the problem prevents a high-quality image from being obtained.
To take an example, a diffusion plate incorporated in light source unit for use in illuminating the film is often placed in a horizontal state and, since the film frequently passes above the diffusion plate or in the neighborhood thereof, the foreign matter such as the dust, dirt, grime or the like is likely to adhere thereto and a scratch is easily produced thereon.
As described above, in the case that the foreign matter such as the dust, dirt or the like adheres to the diffusion plate or the scratch exists therein, since the foreign matter or the scratch appears in a streak form in an image at reading the film with a line scanner, it is easily noticeable; hence, it is likely to be a serious problem. Moreover, unlike the foreign matter or the scratch on the film, the foreign matter which adheres to or the scratch which exists in the diffusion plate appears in all images to be outputted in succession so that the influence thereof will be even greater.